The present invention is directed to a lock for loading and unloading a treatment facility for bulk material operating under an air exclusion or protective atmosphere and particularly for an apparatus for electro-deposition of aluminum from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte. The lock comprises at least one U-shaped lock chamber fillable with an inert fluid and chargeable with inert gas, and a conveying means for conducting a bulk material through the lock along a defined conveyor path.
Aluminum deposited from aprotic, oxygen-free and water-free, aluminum-organic electrolyte is distinguished by its ductility, low number of pores, corrosion resistance and ability to be anodized. Since, due to the reaction with atmospheric oxygen and atmospheric humidity, the access of air effects a considerable reduction in the conductivity and in the useful life of the electrolytes, the electro-plating must be undertaken in a treatment facility or apparatus working under air exclusion or a protective atmosphere. Pretreatment baths required for the surface pretreatment of the material to be electro-plated and after treatment baths required for freeing the aluminized material from electrolyte residues and/or hydrolysis products are likewise maintained in a treatment apparatus operating under a protective atmosphere or air exclusion. Other examples of applications for such treatment facilities, which are closeable and air-tight, are galvanizing, polishing and cleaning processes, wherein the corresponding baths develop, for example, toxic or explosive gasses or produces gasses or vapors which jeopardize the environment in some other way. In order to prevent the access of air or the emission of gasses or vapors when loading and unloading, these treatment apparatuses or facilities operate under an air exclusion and require admission and discharge locks, which are constructed as gas locks, as liquid locks or as a combination gas and liquid lock. These locks are also provided with conveying means for conducting the material to be treated through the lock.
European Patent Application No. 00 13 874 discloses a facility operating under air exclusion for the electro-deposition of aluminum from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte, wherein the material to be aluminized is introduced into an electro-plating tank containing the electrolyte through a liquid lock and is, in turn, likewise removed through a liquid lock. The liquid lock is composed of a U-shaped lock chamber filled with an inert fluid, which is preceded at an admission side of the lock by an antechamber provided with a door, which can be closed gas-tight and which chamber contains an inert gas. For the purpose of loading the apparatus, racks carrying the goods, which are to be electro-plated, are introduced into the antechamber by the door which closes gas-tight and are then suspended from a conveyor means, which comprises two endless conveying chains. During inward transfer, the racks of goods then traverse the antechamber and the lock chamber filled with the inert fluid and the inert gas space arranged in the electro-plating tank above the electrolyte level whereupon they are immersed into the electrolyte. The discharge of the goods at the discharge lock occurs in a reverse direction after the aluminization process.
The lock of this known facility is equipped with an involved and complicated conveyor means which, moreover, only allows throughput of racks of goods. Racks of goods, however, are uneconomical for aluminum-plating bulk materials such as bolts, nuts, screws, spacer bushings and the like because of the loading of these goods to be aluminum-plated into the racks would be extremely work intensive and, therefore, extremely expensive.
U.S. Pat. No. 4,427,518, which claims priority from the same German application as European Patent No. 00 70 011, discloses another apparatus operating under the air exlcusion for the electro-depositing of aluminum from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte. As disclosed in this patent, which is incorporated by reference thereto, the apparatus includes an electro-plating drum, which is arranged in a rotatable fashion in an electro-plating tank having an introduction liquid lock and a discharge lock, which is also a liquid lock. The goods, which are to be aluminized, are introduced into the electro-plating drum by first being introduced through the admission or introduction lock and after traversing the electro-plating drum, which is provided with a helical rib on the inside wall as the conveying means, are then discharged through the discharge lock. The material to be aluminized is introduced into the admission lock, which has an admission funnel that discharges onto a conveyor belt which conveys the goods through the admission lock and discharges them into a funnel which discharges into the beginning or front end of the electro-plating drum. At the back end of the electro-plating drum, a conveyor belt, which begins under the electrolyte level has another end that extends above the electrolyte level. The upper end of this conveyor belt discharges the goods into a funnel-shaped part which discharges onto a portion of another conveyor belt which dips into an inert fluid. This second or other conveyor belt ends above the inert fluid level and discharges through another funnel-shaped outlet nozzle. This known facility has the advantage that bulk goods can be aluminum-plated in a continuous process without having to be loaded into racks for goods. The conveying means for conducting aluminized material through the admission lock and the discharge lock, however, also are relatively complicated. Moreover, the use of conveyor belts requires a seal for the drive shafts which must be conducted out of the lock and the seals for the rotating parts can be difficult to produce due to the high demands that will occur with the particular liquids being utilized.